Digital oxygen index tester Polyurethane oxygen index experiment

Polyurethane is the abbreviation of polyurethane, which is an insulation material widely used in the construction industry and industrial equipment, and an important material in the automotive, shipbuilding, packaging, and other industries. However, due to the special structure of polyurethane foam itself, it is extremely easy to burn, and its oxygen index is only about 17%. The oxygen index is one of the signs to determine its flame retardant properties. The digital oxygen index meter is a test instrument for measuring the oxygen index of polyurethane.

Shanghai Qianshi Precision Electromechanical Technology Co., Ltd. was established in 2012. It focuses on the research and development, design, and production of textile testing instruments, and provides textile testing instruments and services for academic research units and testing institutions. Shanghai Qianshi is currently one of the most competitive R&D textile testing instrument manufacturers in China. The R&D team is composed of a group of experienced engineers. We are committed to serving customers wholeheartedly and striving to promote the technological innovation of textile testing instruments.

In addition, our R&D engineers said that the polyurethane oxygen index test will be affected by environmental conditions, operators, sample preparation differences, and other factors.

1.Influence of state adjustment time

According to the requirements of national standard GB/T2918-1988, the state of the test material is adjusted to minimize the influence of accidental environmental factors on the test results. Therefore, the prepared TDCPP flame-retardant polyurethane foam samples are selected for comparison test, and the temperature and humidity of the constant temperature box are adjusted to a certain value required by the national standard (temperature: 23℃; relative humidity: 50%; air pressure: 86~106kPa). It can be seen from the test data that with the increase in sample adjustment time, the average value of the oxygen index obtained in the test continues to decrease. When the adjustment time meets a certain time*, the oxygen index remains stable. The test results of samples under different adjustment times are different. Therefore, the samples should be strictly adjusted according to the standard requirements, and then tested, to obtain accurate oxygen index values under standard state adjustment time.

2. Influence of sample ignition method

According to GB/T2406-93, two ignition methods are used to test the oxygen index of TDCPP flame-retardant polyurethane foam samples, and the ignition time is 15s.

Top ignition method: make the visible part of the flame contact the top of the sample and cover the entire top surface, and do not let the flame touch the edges and side surfaces of the sample.

Diffusion ignition method: fully lower and move the igniter so that the visible part of the flame is applied to the top surface and vertical side surface of the sample for about 6mm at the same time.

The results show that when the same material is tested under the same conditions, different ignition methods have almost no effect or little effect on the oxygen index measurement data, which is not enough to change the evaluation of the sample oxygen index results. Regardless of the ignition method, when to remove the ignition source and start timing is to intuitively judge the ignition situation of the sample by the naked eye. There is a certain error, which may cause an impact on the inspection data. Only by increasing the number of tests can the error be minimized. In actual operation, it is more labor-saving to use the top ignition method when igniting the sample.

3. Influence of sample length

The sample length of the tested product in the national standard is 70-150mm, to keep consistent with the length of the glass cylinder of the test instrument so that the oxygen concentration in the small environment mixed gas in the glass cylinder is uniform and constant.

It can be seen that the sample length has a great influence on the test data. Within the range required by the national standard, the measured oxygen index value increases continuously with the increase of the sample length. When the sample length is short, there is still a considerable distance between the combustion area of the sample under test and the top of the cylinder. Therefore, the oxygen required for its flame combustion is supported by the instrument itself and is not affected by the airflow outside the cylinder. However, as the sample length increases, the distance between the combustion area of the sample under test and the top of the cylinder becomes shorter, and the flow of oxygen required for flame combustion is gradually affected by the airflow outside the cylinder. To support flame combustion, the instrument itself must provide more oxygen to meet the flame combustion, resulting in a gradual increase in the measured oxygen concentration value. Therefore, the length of the sample under test should be specified as a specific value rather than a range value to reduce the influence of indoor ambient airflow on the combustion condition in the instrument cylinder.

4. The influence of flame retardants

As an expensive additive in polyurethane foam, flame retardants play a very important role. The more flame retardants are added, the better. The influence of the amount of flame retardants added on the physical and mechanical properties of the foam should also be considered. Given factors such as cost, safety, meeting flame retardant technical indicators, and physical and mechanical properties of foam, the use of appropriate flame retardants should be optimized to maximize their effect.

Effect of flame retardant addition: Data show that for TDCPP flame retardant, based on polyether polyol, 10Phr of TDCPP can make the oxygen index of PUF less than 23%. The oxygen index of PUF increases with the increase of flame retardant addition, but after the amount of TDCPP is greater than 15Phr, the oxygen index of the sample is increased very limitedly when the amount of TDCPP is increased.

Effect of different flame retardants: Different flame retardants have different flame retardant effects in polyurethane foam. With the change of flame retardant content, the change law of flame retardant effect is also different. This is mainly affected by the difference in the type of flame retardant and the compatibility of flame retardant with polyurethane foam.

2024-11-26 11:18